1. Field of the Invention
The present invention relates to image recorders, in particular to an image recorder with a laser source, a light modulator, an illumination optical system, and an imaging optical system.
2. Description of the Background Art
Light modulators for use in such an image recorder include, for example, a grating light valve, a digital micromirror device, and a PLZT (lead lanthanum zirconate titanate) light modulator.
The grating light valve is a light modulator (light valve) which modulates a light beam through the use of diffraction caused by several thousands of horizontally aligned reflection plates (ribbons) being moved by electric force. The Grating Light Valve is also called xe2x80x9cGLVxe2x80x9d, being developed by the U.S.-based Silicon Light Machines (Sunnyvale, Calif.) (the Grating Light Valve is a trademark of the Silicon Light Machines).
The digital micromirror device is a light modulator, also called the xe2x80x9cDMD (trademarked by Texas-Instruments),xe2x80x9d which modulates a light beam by electrically tilting several hundreds or several thousands of tilting micromirrors to change the direction of light beams reflecting from the micromirrors.
The PLZT (lead lanthanum zirconate titanate) light modulator is a light modulator which has the function of rotating the polarization state of a laser beam in accordance with a voltage applied thereto and is used in combination with a polarizer or the like.
The conventional image recorders using such light modulators have a problem of not being able to detect a malfunction in a light modulator caused by a breakdown of the light modulator itself or of a driver, etc. of the light modulator.
Especially when the image recorders use, as signal light, outgoing light from a light modulator with no drive signal applied, a laser beam will be kept applied onto the image recording surface even at the occurrence of a malfunction in the light modulator.
For example, when image recording is performed with the application of a laser beam onto a recording medium such as a thermal (heat-sensitive) material, a high-power laser light source such as a bar laser (broad-area semiconductor laser) is used. The use of such a high-power laser light source yields an extremely high power density of a laser beam on the image recording surface; therefore, if the laser beam is kept applied onto the image recording surface, the recording medium might burst into flames, causing a fire.
The present invention is directed to an image recorder for modulating a laser beam emitted from a laser light source by a light modulator and then focusing the laser beam onto an image recording surface to form an image.
According to a aspect of the present invention, the image recorder comprises: a laser light source for emitting a laser beam; a light modulator for modulating a laser beam; an illumination optical system for irradiating the light modulator with a laser beam emitted from the laser light source; an imaging optical system for focusing signal light onto the image recording surface to form an image, the signal light being outgoing light from the light modulator with no drive signal applied to the light modulator; a photodetector for detecting non-signal light which is outgoing light from the light modulator with a drive signal applied to the light modulator; and a detector for detecting a malfunction in the light modulator on the basis of output from the photodetector.
This image recorder can detect a malfunction in the light modulator with certainty. This prevents the occurrence of fogging of a photosensitive material, a fire, or the like in the recording medium which is caused by the laser beam being kept applied onto the image recording surface.
According to another aspect of the present invention, the image recorder further comprises a light shielding mechanism for, when the detector detects a malfunction in the light modulator, cutting off an optical path between the laser light source and the image recording surface under the control of the controller.
Since the optical path between the laser light source and the image recording surface is cut off when the detector detects a malfunction in the light modulator, the occurrence of fogging of a photosensitive material, a fire, or the like in the recording medium can be prevented.
According to still another aspect of the present invention, the image recorder further comprises a stop mechanism for, when the detector detects a malfunction in the light modulator, turning off the laser light source under the control of the controller.
Since the laser light source is turned off when the detector detects a malfunction in the light modulator, the occurrence of fogging of a photosensitive material, a fire, or the like in the recording medium can be prevented.
An object of the present invention is, therefore, to provide an image recorder which allows easy malfunction detection in the light modulator and can prevent the occurrence of a fire or the like.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.